---
title: "A2A Security | Kastrax Docs"
description: "Detailed guide on security mechanisms in the Agent-to-Agent (A2A) protocol."
---

# A2A Security ✅

Security is a critical aspect of the A2A protocol, ensuring that agent communications are protected and that only authorized agents can access capabilities. This guide explains the security mechanisms in the Kastrax A2A implementation.

## Security Overview ✅

The Kastrax A2A protocol implements several security mechanisms:

1. **Authentication**: Verifying the identity of agents
2. **Authorization**: Controlling access to capabilities
3. **Encryption**: Protecting data in transit
4. **Rate Limiting**: Preventing abuse
5. **Audit Logging**: Tracking agent interactions
6. **Input Validation**: Preventing injection attacks

## Authentication Methods ✅

The A2A protocol supports multiple authentication methods:

### API Key Authentication ✅

API key authentication is the simplest method:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    val a2aInstance = a2a {
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with API key authentication"
            
            // Configure API key authentication
            authentication {
                type = AuthType.API_KEY
                details = mapOf(
                    "header" to "X-API-Key"
                )
            }
            
            // Define capabilities...
        }
        
        // Configure server with security
        server {
            port = 8080
            enableCors = true
            
            // Configure API keys
            apiKeys = mapOf(
                "client1" to "api-key-1",
                "client2" to "api-key-2"
            )
        }
    }
}
```

### JWT Authentication ✅

JWT (JSON Web Token) authentication provides more advanced security:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import ai.kastrax.a2a.security.JwtConfig
import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    val a2aInstance = a2a {
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with JWT authentication"
            
            // Configure JWT authentication
            authentication {
                type = AuthType.JWT
                details = mapOf(
                    "issuer" to "kastrax-a2a",
                    "audience" to "secure-agent"
                )
            }
            
            // Define capabilities...
        }
        
        // Configure server with JWT security
        server {
            port = 8080
            enableCors = true
            
            // Configure JWT
            jwt {
                secret = "your-jwt-secret" // In production, use a secure secret
                issuer = "kastrax-a2a"
                audience = "secure-agent"
                expirationMs = 3600000 // 1 hour
            }
        }
    }
}
```

### OAuth2 Authentication ✅

OAuth2 authentication enables integration with external identity providers:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import ai.kastrax.a2a.security.OAuth2Config
import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    val a2aInstance = a2a {
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with OAuth2 authentication"
            
            // Configure OAuth2 authentication
            authentication {
                type = AuthType.OAUTH2
                details = mapOf(
                    "issuer" to "https://auth.example.com",
                    "audience" to "secure-agent"
                )
            }
            
            // Define capabilities...
        }
        
        // Configure server with OAuth2 security
        server {
            port = 8080
            enableCors = true
            
            // Configure OAuth2
            oauth2 {
                issuer = "https://auth.example.com"
                audience = "secure-agent"
                jwksUrl = "https://auth.example.com/.well-known/jwks.json"
            }
        }
    }
}
```

## Authorization ✅

Authorization controls which agents can access which capabilities:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import ai.kastrax.a2a.security.Role
import ai.kastrax.a2a.security.Permission
import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    val a2aInstance = a2a {
        // Define roles
        role("reader") {
            permission(Permission.READ)
        }
        
        role("writer") {
            permission(Permission.READ)
            permission(Permission.WRITE)
        }
        
        role("admin") {
            permission(Permission.READ)
            permission(Permission.WRITE)
            permission(Permission.ADMIN)
        }
        
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with role-based authorization"
            
            // Configure authentication
            authentication {
                type = AuthType.API_KEY
            }
            
            // Define a capability with role-based access
            capability {
                id = "get_sensitive_data"
                name = "Get Sensitive Data"
                description = "Gets sensitive data that requires authorization"
                
                // Require admin role
                requiredRole = "admin"
                
                // Define parameters...
                
                returnType = "json"
            }
            
            // Define a capability with lower access requirements
            capability {
                id = "get_public_data"
                name = "Get Public Data"
                description = "Gets public data that requires minimal authorization"
                
                // Require reader role
                requiredRole = "reader"
                
                // Define parameters...
                
                returnType = "json"
            }
        }
        
        // Configure server with role assignments
        server {
            port = 8080
            enableCors = true
            
            // Configure API keys with roles
            apiKeys = mapOf(
                "client1" to Pair("api-key-1", "reader"),
                "client2" to Pair("api-key-2", "writer"),
                "admin" to Pair("admin-api-key", "admin")
            )
        }
    }
}
```

## Encryption ✅

The A2A protocol uses HTTPS to encrypt data in transit:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import ai.kastrax.a2a.security.TlsConfig
import kotlinx.coroutines.runBlocking
import java.io.File

fun main() = runBlocking {
    val a2aInstance = a2a {
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with HTTPS encryption"
            
            // Configure authentication
            authentication {
                type = AuthType.API_KEY
            }
            
            // Define capabilities...
        }
        
        // Configure server with HTTPS
        server {
            port = 8443
            enableCors = true
            
            // Configure TLS
            tls {
                keyStore = File("keystore.jks")
                keyStorePassword = "password"
                keyAlias = "a2a-server"
                privateKeyPassword = "password"
            }
        }
    }
}
```

## Rate Limiting ✅

Rate limiting prevents abuse of the A2A API:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import ai.kastrax.a2a.security.RateLimitConfig
import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    val a2aInstance = a2a {
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with rate limiting"
            
            // Configure authentication
            authentication {
                type = AuthType.API_KEY
            }
            
            // Define capabilities...
        }
        
        // Configure server with rate limiting
        server {
            port = 8080
            enableCors = true
            
            // Configure rate limiting
            rateLimit {
                requestsPerMinute = 60 // 1 request per second
                burstSize = 10 // Allow bursts of up to 10 requests
                
                // Configure per-client limits
                clientLimits = mapOf(
                    "client1" to 30, // 30 requests per minute
                    "client2" to 120 // 120 requests per minute
                )
            }
        }
    }
}
```

## Audit Logging ✅

Audit logging tracks all agent interactions:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import ai.kastrax.a2a.monitoring.AuditLogConfig
import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    val a2aInstance = a2a {
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with audit logging"
            
            // Configure authentication
            authentication {
                type = AuthType.API_KEY
            }
            
            // Define capabilities...
        }
        
        // Configure monitoring with audit logging
        monitoring {
            // Configure audit logging
            auditLog {
                enabled = true
                logRequests = true
                logResponses = true
                sensitiveFields = listOf("password", "apiKey", "token")
                
                // Configure storage
                storage = "file" // Options: "file", "database", "cloud"
                filePath = "logs/audit.log"
                
                // Configure retention
                retentionDays = 90
            }
        }
    }
}
```

## Input Validation ✅

Input validation prevents injection attacks:

```kotlin
import ai.kastrax.a2a.a2a
import ai.kastrax.a2a.agent.a2aAgent
import ai.kastrax.a2a.model.AuthType
import ai.kastrax.a2a.model.JsonObject
import ai.kastrax.a2a.validation.ParameterValidator
import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    val a2aInstance = a2a {
        a2aAgent {
            id = "secure-agent"
            name = "Secure Agent"
            description = "An agent with input validation"
            
            // Configure authentication
            authentication {
                type = AuthType.API_KEY
            }
            
            // Define a capability with schema validation
            capability {
                id = "process_data"
                name = "Process Data"
                description = "Processes data with strict validation"
                
                // Define a parameter with a JSON schema
                parameter {
                    name = "data"
                    type = "object"
                    description = "Data to process"
                    required = true
                    schema = JsonObject(
                        mapOf(
                            "type" to JsonPrimitive("object"),
                            "required" to JsonArray(listOf("id", "value")),
                            "properties" to JsonObject(
                                mapOf(
                                    "id" to JsonObject(
                                        mapOf(
                                            "type" to JsonPrimitive("string"),
                                            "pattern" to JsonPrimitive("^[a-zA-Z0-9_-]+$") // Alphanumeric only
                                        )
                                    ),
                                    "value" to JsonObject(
                                        mapOf(
                                            "type" to JsonPrimitive("string"),
                                            "maxLength" to JsonPrimitive(1000)
                                        )
                                    )
                                )
                            )
                        )
                    )
                }
                
                // Define return type
                returnType = "json"
            }
            
            // Implement capability handler
            handler("process_data") { request ->
                // Parameters are automatically validated against the schema
                // If validation fails, an error response is returned
                
                // Process the validated data
                val data = request.parameters["data"]?.jsonObject
                
                // Return result
                InvokeResponse(
                    id = request.id,
                    result = buildJsonObject {
                        put("status", JsonPrimitive("success"))
                        put("message", JsonPrimitive("Data processed successfully"))
                    }
                )
            }
        }
    }
}
```

## Security Best Practices ✅

When implementing A2A security, follow these best practices:

1. **Use HTTPS**: Always use HTTPS in production to encrypt data in transit
2. **Implement Authentication**: Choose an appropriate authentication method for your use case
3. **Apply Authorization**: Use role-based access control to restrict capability access
4. **Validate Input**: Use schema validation to prevent injection attacks
5. **Implement Rate Limiting**: Protect your API from abuse
6. **Enable Audit Logging**: Track all agent interactions for security monitoring
7. **Rotate Secrets**: Regularly rotate API keys, JWT secrets, and other credentials
8. **Minimize Attack Surface**: Only expose necessary capabilities
9. **Apply Principle of Least Privilege**: Grant minimal permissions required for each agent
10. **Monitor for Suspicious Activity**: Set up alerts for unusual patterns

## Next Steps ✅

Now that you understand A2A security, you can:

1. Learn about [multi-agent systems](./multi-agent-systems.mdx)
2. Explore [A2A workflows](./a2a-workflows.mdx)
3. Implement [A2A monitoring](./a2a-monitoring.mdx)
